• Journal of Powder Materials
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• v.8 no.3
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• pp.210-213
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• 2001

$Si_3N_4$/TiN nano/nano-type composites were successfully fabricated by the combination of a mechano-chemical grinding (MCG) method and a short time sintering process, and their wear resistance was evaluated. Powder mixtures of $\alpha-Si_3N_4$and Ti were prepared using mechano-chemical grinding process and the resulting nanocomposite powder mixtures were consolidated using pulsed electric current sintering (PECS). TEM observation showed that the nano/nano-type composites consisted of homogeneous and very fine matrix grains with the size less than 100 nm. The obtained $Si_3N_4$-based nano/nano-type showed high wear resistance and electric discharge machinability.

• Journal of Technologic Dentistry
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• v.40 no.1
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• pp.27-32
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• 2018

Purpose: This study was performed to investigate processability of the dental zirconia block. Most of the CAD/CAM zirconia restorations utilize the partially sintered blocks, which are sintered at a temperature lower than $1100^{\circ}C$. Methods: Partially sintered zirconia samples were prepared $40{\times}30{\times}10mm$ and surface treatment by #2000 sandpaper. Scratch hardness was determined by the procedure of ASTM G171-03 using a scratch hardness tester(KS TECH, Korea) equipped with a real time load detector to measure tangential force during scratching. The scratch rate was 30 mm/min. Results: Scratch hardness(Hs) increases steeply with increase in the loads. The highest Hs was sampl 1.42 GPa and lowest was sample 0.42 GPa. Conclusion : The machinability of partially sintered CAD/CAM zirconia blocks can be optivized by manipulation of Hs.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1052-1053
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• 2006

Aluminum-based composites reinforced with various amounts of $\alpha-Si_3N_4$ were produced by powder metallurgy (P/M). The machinability properties of $MMC_s$ were determined by means of cutting forces and surface roughness. Machining tests were carried out by using PCD and K10 tools. Increasing of $Si_3N_4$ volume fraction in the matrix resulted in a decrease of the surface roughness and turning forces. PCD cutting tools showed better cutting performance than K10 tools.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.292-296
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• 2002

In the present investigation, the improvement of processing efficiency in the high speed machining of GC250 is explored. This study is to evaluate the tool performance in difficult-to-material using the new developed tool. Tool performance evaluation are conducted by tool wear, surface roughness, chattering in machined surface. The tool wear of A type was smaller than B type. In type B tool the chatter mark was observed in machined surface. The good surface roughness was obtained in type A tool. Consequently, the tool performance of A type is better than B type.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.2
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• pp.51-57
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• 2008

Recently, the manufacturer of microscopic structures along with the development of technology to produce electronics, communication and semiconductors allows various components to be smaller in size, with higher precision. Therefore, preoccupancy of micro/nano-level machining technology in order to product micro/nano-components and parts is key issue in the field of manufacturing. In this study, machinability of micro machining was studied through the machining of aluminum, brass and steel workpiece. Inspection of the cutting force variation patterns of large numbers of micro machining indicated that characteristics of the workpiece. Surface roughness prediction methods were developed by considering the variation of the static part of the feed direction cutting force. The accuracy of the proposed approaches were tested with experimental data and the agreement between the predictions and actual observations are addressed.

• Journal of the korean Society of Automotive Engineers
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• v.12 no.2
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• pp.59-70
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• 1990

Crack of breaking toughness of most Ceramics material is 1-5MPa .root.m but that of Zirconia Ceramics is improved to be 6-8MPa .root.m and its development of machining difficult-to-machine material is on the rise as urgent subject. For general Zirconia Ceramics machining, diamond grinding wheel is generally used by selecting an appropriate one and establishing grinding condition but due to such limitations as economics, grinding efficiency and machining geometry, great interest in machining method being used for diamond tool is emphasized. But it is reported that diamond tool is oxidized by cutting heat in the air and is graphitized in vacuum, which causes bad effects on tool life. In this study, to restraint cutting heat the internal side of tool is cooled, and restraint low temperature cooling system and being experimented. Further, the machinability of diamond tool for Zirconia Ceramics machining is analyzed with respect to tool wear and stress.

• Journal of the Korean Society for Precision Engineering
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• v.8 no.1
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• pp.63-73
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• 1991

Carbon fiber epoxy composite materials are widely used in the structures of aircrafts, robots and other machines because of their high specific strength, high specific stiffness and high damping. In order for the composite materials to be used in aircraft structures or machine elements, accurate surfaces for bearing mounting or joints must be provided, which require precise machining. In this paper, the machinability of the carbon fiber epoxy composite materials in turning was experimentally investigated. The cutting mechanism and the Taylor Tool Wear constants were determined and the surface roughness was measured w.r.t. cutting speeds and feed rates.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.11
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• pp.55-62
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• 2000

The poor machinability material such as austenite stainless steel(STS304) is emphasized on the wide use of HSSE for the tapping operation. The difficulty can be entirely to tapping torque due to chip formation through the hole of tap. The object of this study is to investigate tap geometry affecting the tapping torque from a practical point of view. The study shows that the optima tapping torque is affected by the tap geometry and cutting condition for STS304.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.205-206
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• 2010

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2001.04a
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• pp.17-17
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• 2001